I don't think I've ever run a pregnant women baby sacrifice cult.
I would look at a DM wanting to run that a little bit sideways.
In a game with Illithids, Slaad, Succubi, dominate person spells, and official books detailing infernal and demonic cults, this isn't that far out for me. It depends on how it is run. I mean, look at that official lore on how hags procreate. Look into the description on how orcs increase their numbers.
That said, I would never dive into these scenarios at a convention or open-to-the-public game at a FLGS. I think games like this could be okay in such contexts, with proper warning in the game description, but even then, just because the group at your table may agree to it. Those on nearby tables may not appreciate overhearing it.
But even if I keep things very PG rated, you have people who are afraid of snakes and insects. I had a friend in high school, who, although he was a big imposing guy, got really creeped out about bugs. Like, when when you'd get these large numbers of box elder bugs swarming in the fall near doors, he couldn't go in or out of that door. He would also leave the room if insect swarms came up in a game. I've also worked in a museum of natural history and have seen on multiple occasions people physically recoil and freak out when they came across a snake exhibit.
Phobias are so personal, that it is very difficult to anticipate everyone that might come up when you open a game to a group of strangers. Short of listing every every type of creature and environment challenge that can come up in an encounter in the description of the game, I really don't know how these kinds of consent rules would work.
In a recent AL game there there was a flash flood challenge. At least a half hour was spend making saves and athletic checks to avoid drowning and saving party members who were drowning. What if one of the players almost drowned as a child and was afraid of water? What if someone had a loved one who drowned? As a DM, I
WANT to be empathetic and help them enjoy the game.
If the affected player just touches and X, I suppose I could suss out that the entire flood scene is an issue. But I would prefer someone to just say, I'm not comfortable with a flooding/drowning scene rather than playing a guess-what-I'm-uncomfortable-with game. I find some of these "solutions" to the issue to be more awkward than what they are trying to solve.
But once I know what the issue is, sure, I can work around that. I can skip that scene. It may mean a shorter game and some of the other players may be disappointed, but I think most people would be sympathetic.
But what is someone joins an AL game and the adventure is underwater themed. The entire adventure involves infiltrating a sahuagin lair and overcoming them and their shark minions. Now, most of times I've showed up for AL games in my FLGS, I don't know what the adventure is going to be. So a person could easily join a came that will touch upon a phobia. In this specific sahuagin adventure, touching an X isn't going to help. Is the person afraid of water or sharks? Furthermore, let's say the person explains to the DM that they survived a shark attack and find describing attacks by sharks to be traumatic. Is that DM now supposed to scrap the adventure he or she prepared?
It really sucks for that person to have to walk away from the game, but in this situation, the content is not inappropriate for a general audience, including young adults or even older children. Nobody is singling out the individual. There is no bullying. It is just an unfortunate coincidence that the adventure content conflicts with that personal phobia/past trauma. Hopefully there is another game being run at that time the person can join in on--I'd certainly speak to the other DMs and try to find a spot for this person. But I don't expect a DM to scrap that adventure and have a back-up ready to go.